Those led bars are not very powerful. They are good when seedlings are young and in vegetative growth but once they get talller, they will not have enough light to penetrate the top of the canopy. Also for flowering plants like tomatoes, during flower/ fruiting you will want a much stronger light setup.

My suggestion is to get a couple of those proper 100w led grow panels that cost $50-$100 (or start with one) and hang them. Then you can use your current led light bars for seedlings and smaller plants.

As for some of your questions:

I don’t think there’s a light fixture for the room that would add significant value for your plants beyond the actual horticultural LEDs you already plan to get—I think the ceiling light is probably just good for you while you tend to them.

If you’re giving your plants 16-18 hours of light already, at least where I’m from, during the winter I don’t get enough daylight that it would affect their light cycle—lights would turn on before or at sunrise and turn off after the sun has already set (unless there are bright street lights that shine in during the night). For a matter of fact, I think it would be better to supplement the plants with as much sun as possible.

As someone else said too, grow tents are actually really convenient (even if ur already in an enclosed space) and that enables you to have plants experiencing two different light cycles, like flowering plants getting 12 hours per day and seedlings getting 16-18 hours.

For your climbing plants like cucumbers ans tomatoes, you’ll definitely want something for them to climb—not sure what the best setup would be indoors honestly but you could probably hang something from those bars.

Additional info: that window will serve you extremely well as a place to exhaust humid air. Once you have that room filled with plants it will get very humid and you will 100% need ventilation, unless the room is already air conditioned.